Highly pressurized chambers are used in a variety of industries in the processing of organic or inorganic substances and can operate at pressures from 2000 to over 7,000 times atmospheric pressure. In the pharmaceutical and biotechnology industries, high-pressure processing is used to inactivate, sterilize or modify biological substances, to include a variety of medicines and drugs, for example.
In the food industry, pressure chambers are used to process food substances to inactivate pathogens and microorganisms in the food. Pressure treating food substances does not expose foods to the potentially damaging effects of high temperatures and therefore helps to improve the food's palatability, nutritional quality, texture, color, and can also be used as a means of preservation without adding preservatives. High-pressure treatment may take place at initial product temperatures ranging from below room temperature to temperatures approaching 100 C. Pressure treated food substances such as ready-to-eat meats, prepared vegetables, fruit juices, and other products have benefited from high-pressure processing.
Pressure processing can have significant benefits in terms of changed protein function, enhanced or reduced enzyme action, and cellular membrane destruction. These effects can lead to the inactivation of certain microorganisms. Small macromolecules that are responsible for flavor, color, odor, and nutrition, are typically not changed by pressure. An article by Avure Technologies, <http://www.fresherunderpressure.com/science_hpp_review.htm>, discusses the uses, benefits, mechanisms, advantages, and remaining considerations regarding high-pressure processing.
High-pressure processing compresses and dissolves gas present in the product, thus rapid depressurization may result in greater cellular damage due to a rapid expansion of the gas. Controlled depressurization can control the texture of the resulting product. Also, since pressure is one of the primary thermodynamic variables controlling complex biomolecular structure, high-pressure can be used to modify biomolecular conformation state. Some biomolecules have high sensitivity to variations in temperature or pressure. Thus the use of high-pressure to process these substances requires the precise control of processing parameters though out the processing cycle. These parameters include: pressure, temperature, time at pressure, rate of pressurization, and rate of depressurization. The ability to reduce pressure in a controlled manner allows for delicate structures to remain near equilibrium. For example, dissolved gas will be able to diffuse from structures without cellular rupture and meta-stable conformational molecular states may be better retained.
The current approach used to depressurize a high-pressure chamber is to open a small orifice and allow the pressure to rapidly decrease by venting fluid from the pressure chamber through the small orifice. This approach achieves a depressurization time of only a few minutes, which is not slow enough to prevent structure disruption. The use of direct venting also is more difficult when the processing volume is small. Even a small leak will cause a significant loss of pressure.
For processing large volumes, multiple orifices can be used to extend the depressurization time to a period of hours (i.e., approximately one hour or more). The number of orifices will be increased as the pressure is reduced to maintain the selected depressurization rate. Accordingly, this is a complex approach and could involve a large number of high-pressure components. Thus, there is a need for an improved system and method to control the depressurization rate of substances during the depressurization of a high-pressure operation.